1. Field of the Invention
The present invention relates to coke oven batteries and, more particularly, to an electro-mechanical interlock system for the gates on the usual coal bunker and the controls for operating the larry car along the top of the coke oven battery.
2. Description of the Prior Art
It is customary to provide a large coal bunker at one end of a coke oven battery that is supplied with coal by a belt conveyor carrying coal from a coal pile, located at some distance from the battery, to the coal bunker. The coal bunker is so designed that the conventional larry car can be located under the coal bunker from which coal is discharged into the coal hoppers on the larry car.
The coal bunker usually has a number of discharge gates, equal to the number of coal hoppers on the larry car, that are shear gates of the counterweighted type. Most of the in-service conventional larry cars have a travel control circuit interlocked with a loading rack on the larry car that opens the bunker gates when the larry car is properly spotted under the bunker. Thus, the larry car, in theory at least, cannot travel as long as the loading rack and the bunker gates are in the open position.
Despite the fact that the loading rack may be interlocked with the travel circuit of the larry car, the loading rack can be closed and the larry car can move while the bunker gates are still open. This results in a major coal spillage. These major coal spills generally result in the loss of production in the battery and in a very costly cleanup project.
Some operators of coke oven batteries have tried various devices to prevent the travel of the larry car while the bunker gates are open. Such devices have included mechanical limit switches on the gate frame to shut off the electrical power to the larry car while the gates are open. But, despite such preventive devices that have tried, major coal spills still are a serious problem in coke oven battery operations.
Usually the major coal spills occur because (1) the gates do not close because a counterweight is used and it is not a reliable device to move the gates from open to closed position; (2) the design of "dogs" on the loading rack and the gate frame make it easy for the loading rack "dog" to slip past the "dog" on the gate frame without closing the gates; and (3) the difference in vertical height of a loaded larry car compared to an empty larry car makes it practically impossible to maintain limit switch connection between the gate frame and the larry car.
Those skilled in the art will recognize, however, from the following description of one embodiment of the present invention how it ensures a proper interlock between the bunker gates and the electrical travel control circuit of the larry car, and thereby avoids such costly coal spills.